CONSTITUENTS OF THE BIOSPHERE 



39 



C 



CH, 



/"W"\ 



H:.C,, ijC 



H 

 H, \ 



C' H C 



9 



c 



16 



CH, 



D 



H,C, "C\„ ^CH 



14 C- 



15 



CH, 



H.C 



B 



sC 



CH, 



AA 



C H C 

 Ho Hj 



The natural compounds containing this ring, the steroids, are oxy- 

 genated, alkyl-substituted derivatives of the hydrocarbon, having the 

 following general formula, where R and R' vary from compound to com- 

 pound : 



derived from oestrane 



CH, 



In the biosphere this basic carbon skeleton appears in a series of guises, 

 the most important being the following : 



Substituent group R and R' 

 Cholesterol* 



CHs 



I 

 CH3-CH-(CH2)3— CH(CH3)2 



* The other sterols have double bonds in the side chain or alkyl substituents. 



